The present invention relates to a structure of a V-shaped internal combustion engine comprising a hydraulic pressure control device with respect to the disposition of a hydraulic pressure control valve.
In addition, the present invention also relates to a spool valve body structure comprising a hydraulic pressure controlling spool valve, and more particularly to a spool valve body structure adapted to be mounted on an internal combustion engine which comprises a hydraulic pressure controlling spool valve for controlling the supply of oil introduced under a predetermined hydraulic pressure to required portions via a spool valve.
In the case of a V-shaped internal combustion engine in which banks of cylinders are V-shaped relative to each other, it is the common practice to utilize a space between the V-shaped banks of cylinders for disposition of an intake manifold.
Japanese Unexamined Patent Publication No. Hei. 5-71315 discloses a V-shaped internal combustion engine comprising a variable valve timing control device in which a hydraulic pressure control valve is provided on a cylinder block.
The hydraulic pressure control device in the disclosed patent is disposed substantially at the center of a cylinder block in a direction of a crankshaft between the V-shaped banks of cylinders in such a manner as to protrude therefrom, and an intake manifold is disposed above the hydraulic pressure control valve.
Therefore, the intake manifold has to be disposed so as to avoid any interference with the hydraulic pressure control valve disposed between the V-shaped banks of cylinders, and this results in an increase in the height of the intake manifold by a distance which the hydraulic pressure control valve protrudes from the cylinder block, leading to the enlargement of the internal combustion engine.
In addition, the hydraulic pressure control valve resides between the V-shaped banks of cylinders and is covered with the intake manifold thereabove, this making it difficult to service the hydraulic pressure control valve for maintenance.
On the other hand, an example of conventional spool valve body structures is shown in FIG. 11 which has formed therein a spool valve chamber in which a spool valve is slidably received and an oil introduction chamber communicating with the spool valve chamber via a communication passage. This spool valve body 131 is mounted at an end of a cylinder block in a direction of a crankshaft which block is located between banks of cylinders of a V-shaped internal combustion engine which are laid out in a V-shaped fashion or V-shaped and provided in a valve mechanism for opening and closing intake valves and exhaust valves of the internal combustion engine for use in a hydraulic pressure control device for controlling hydraulic pressures for a variable valve timing switching mechanism for varying actuation timings and lift distances of the valves in response to running conditions of the internal combustion engine (for instance the revolutions of the internal combustion engine).
In this conventional spool valve body structure, the spool valve chamber 132 is formed downwardly from an upper surface of the spool valve body 131 as a bottomed hole having a uniformly circular cross-section. In addition the oil introduction passage 133 is formed upwardly from a lower surface of the spool valve body 131 as a bottomed hole having an axis which is parallel with an axis of the spool valve chamber 132 and a circular cross-section. When mounting the spool valve body on the internal combustion engine, the oil introduction passage 131 is connected to a main gallery formed in the cylinder block of the engine, and oil sent under pressure by an oil pump is supplied into this oil introduction passage 133. Furthermore, a controlling hydraulic pressure passage 134 open to the oil introduction passage 133 is formed downwardly from the upper surface of the spool valve body 131.
On the other hand, three vertically spaced-away lateral holes 161, 162, 163 are formed as a hole as cast in a side 131b of the spool valve body 131. The depth of the upper and middle lateral holes 161, 162 reaches a portion slightly beyond the spool valve changer 132. Of these two holes the upper lateral hole 161 constitutes a relief opening for relieving oil in order to relieve a high pressure supplied to the variable valve timing switching mechanism. The middle lateral hole 162 constitutes a working hydraulic pressure supply opening 162 for actuating the variable valve timing switching mechanism. Furthermore, the working hydraulic pressure supply opening 162 and the controlling hydraulic pressure passage 134 are caused to communicate with each other via a first orifice 131a. The depth of the lower lateral hole 163 reaches a portion slightly beyond the oil introduction passage 133, and this lower lateral hole 163 is intended to constitute a communication passage 164 for establishing a communication between the spool valve chamber 132 and the oil introduction passage 133, an open portion thereof being closed with a plug.
The spool valve 136 is slidably received in the spool valve chamber 132. This spool valve 136 has three lands; an upper land 136b; a middle land 136c; and a lower land 136d, and formed in the spool valve chamber 132 are a first annular chamber 132a partitioned by the upper land 136b and the middle land 136c and a second annular chamber 132b partitioned by the middle land 136c and the lower land 136d. A hole 136e is formed in the spool valve 136 which is open at a lower end and has a ceiling portion at an upper end thereof. This hole 136e has a stepped portion such that a portion corresponding to the lower land 136d constitutes a large-diameter portion and the remaining portion constitutes a small-diameter portion. A spring 137 is provided in the large-diameter portion of the hole 136e between the bottom of the spool valve chamber 132 and the stepped portion for biassing the spool valve upwardly. In addition, a second orifice 136a is formed in the ceiling portion which is open to the upper surface of the spool valve 136. Furthermore, the first annular chamber 132a is caused to communicate with the hole 136e via a communication passage 136f.
When a high hydraulic pressure is not applied to the upper surface of the spool valve 136, the spool valve 136 is situated at an upper position shown in FIG. 11-B by virtue of the biassing force of the spring 137, and therefore the communication passage 164 is closed by the lower land 136b, the first orifice 131a is caused to communicate with the second annular chamber 132b, the relief opening 161 is caused to communicate with the first and second annular chambers 132a, 132b, and the working hydraulic pressure supply opening 162 is caused to communicate with the second annular chamber 132b. On the other hand, when a high hydraulic pressure is applied to the upper surface of the spool valve 136, the spool valve is moved to a lower position against the biassing force of the spring 137, and in this state, the communication passage 164 and first orifice 131a are caused to communicate with the second annular chamber 132b, the relief opening 161 is caused to communicate only with the first annular chamber 132a, and the working hydraulic pressure supply opening 162 is caused to communicate with the second annular chamber 132b.
An electromagnetic valve body 150 is mounted on the upper surface of the spool valve body 131. Formed in this electromagnetic valve body 150 are an inlet passage 152 communicating with the controlling hydraulic pressure passage 134 and an outlet passage 153 communicating with the open end of the spool valve chamber 132 of the spool valve body 131 for supplying hydraulic pressures for application to the upper surface of the spool valve 136. When excited, a valve body 154 of the electromagnetic valve 151 is constructed to be separated from a valve seat therefor so as to establish a communication between the inlet passage 152 and the outlet passage 153, while when de-excited, the valve body 154 is constructed to be seated on the valve seat by a return spring so as to cut off the outlet passage 153 from the inlet passage 152.
A connecting member (not shown) is mounted on a side 131b of the spool valve body by making use of a mounting hole 131c and attached to this connecting member are a pipe communicating with the relief opening 161 and adapted to discharge relief oil and a pipe communicating with the working hydraulic pressure supply opening 162 and connected to the a working hydraulic pressure supply passage for supplying hydraulic pressures to the variable valve timing switching mechanism.
Next, an operation of the spool valve 136 in the spool valve body structure constructed as described above and a flow of oil therethrough will be described. Oil from the main gallery in the cylinder block not shown is supplied to the oil introduction passage 133 and the controlling hydraulic pressure passage 134. With the electromagnetic valve 151 being de-excited and the inlet passage 152 being closed by the valve body 154, since there is applied no high hydraulic pressure to the upper surface of the spool valve 136, the spool valve 136 is located at the upper position by virtue of the spring force of the spring 137. This causes the lower land 136d to close the communication passage 164, and the oil introduction passage 133 is caused to communicate with the second annular chamber 132b via the controlled hydraulic pressure chamber 134 and the first orifice 131a. On the other hand, the working hydraulic pressure supply opening 162 is caused to communicate with the second annular chamber 132b, and the relief opening 161 is caused to communicate with the outlet passage 153 via the first annular chamber 132a, a communication path 136f, the hole 136e and the second orifice 136a, and it is also caused to communicate with the working hydraulic pressure supply opening 162 via the second annular chamber 132b.
In this state, the high hydraulic pressure of the variable valve timing switching mechanism is relieved via the working hydraulic pressure supply passage 162, and the high hydraulic pressure in the outlet passage 153 is also relieved through the second orifice 136a. On the other hand, oil supplied from the first orifice 131a is supplied to the variable valve timing switching mechanism as a low hydraulic pressure via the working hydraulic pressure supply passage to thereby keep the variable valve timing switching mechanism in a non-operational state. Excess oil from the first orifice 131a is discharged via the relief opening 161 as relief oil.
Next, with the electromagnetic valve 151 being excited and the valve body 154 being separated from the valve seat to open the inlet passage 152, since the oil introduction passage 133 communicates with the outlet passage 153 via the controlling hydraulic pressure passage 134 and the inlet passage 152, the spool valve 136 is moved to the lower position against the biasing force of the spring 137 by virtue of the application of high hydraulic pressure in the oil introduction passage 133 to the upper surface of the spool valve 136. This causes the lower land 136d to move downwardly to open the communication passage 164, whereby the oil introduction passage 136 is caused to communicate with the second annular chamber 132b via the communication passage 164, while communicating with the first annular chamber 132a via the outlet passage 153, the second orifice 136a, the hole 136e and the communication path 136f.
In this state, a high hydraulic pressure is supplied to the working hydraulic pressure supply opening 162 via the communication passage 164, and this high hydraulic pressure is then supplied to the variable valve timing switching mechanism via the working hydraulic pressure supply passage to thereby actuate the same mechanism. On the other hand, a part of the oil in the outlet passage 153 is supplied to the relief opening 161 via the second orifice 136a, the hole 136e, the communication path 136f and the first annular chamber 132a and discharged as relief oil.
In the spool valve body structure as described above, there is no chance for the spool valve chamber 132 and the oil introduction passage 133 to overlap each other and they are formed with a bulkhead being interposed therebetween. Therefore, a distance between the axes of the spool valve chamber 132 and the oil introduction passage 133 becomes longer by a distance resulting from the existence of the bulkhead, this enlarging the spool valve body 131 accordingly. This causes a need to avoid an interference of the spool valve body 131 with an intake manifold disposed in line with an axial direction of a crankshaft between V-shaped banks of cylinders of the internal combustion engine. Thus, it was difficult to lay out the devices in a compact fashion.
In addition, the lateral holes are formed as a hole as cast which constitute the relief opening 161, the working hydraulic pressure supply opening 162 and the communication passage 164, and the depths of those lateral holes are deep enough to reach beyond the spool valve chamber 132. Due to this, it is inevitable that the gradient for forming such cored holes increases the opening areas of those openings and the passage in the spool valve body side 131b, and the sizes of portions corresponding thereto of the connecting member that is mounted on this side 131b of the spool valve body are eventually made larger than required functionally. As a result of this, the whole device constituting the oil passage system becomes larger and the spool valve body 131 itself also becomes large. Therefore, from this point it is hard to lay out the devices in a compact fashion.
Furthermore, in order to provide the communication passage 164, the lower lateral hole 163 needs to be formed as a hole as cast, and a plug also needs to be provided so as to close an open portion thereof. Due to this, not only is the spool valve body 131 made large but also man-hours are increased accordingly.